Conyebsion of bwbrocaihbons



Reissue'd May 28, 1940 I UNITED STATES CONVERSION OF HYDROOARBONS JacqueC. Morrell, Chicago,

Ill.,assignor to Universal Oil Products Company, Chicago, 11]., acorporation of Delaware No Drawing. Original No. 2,124,583, dated July26, 1938, Serial No. 103,393, September 30, 1936. Application forreissue September 15, 1939, Se-

rial No. 295,107

8 Claims. (Cuzco-66s) version of any given paraflin or other aliphatic 7This invention relates particularly to the conversion of straight chainhydrocarbons into closed chain or cyclic hydrocarbons.

More specifically, it is concerned with a process involving the use ofspecial catalysts and specific conditions of operation in regard totemperature, pressure and time of reaction whereby aliphatichydrocarbons can be efllciently converted into aromatic hydrocarbons.

In the straight pyrolysis of pure hydrocarbons .or hydrocarbonmixturessuch'as those encountered in fractions from petroleum or othernaturally occurring or synthetically produced hydrocarbon mixtures thereactions involved which produce aromatics from parafllns and olefinsare of an exceedingly complicated character and cannot be very readilycontrolled.

It is generally recognized that, in the thermal decomposition ofhydrocarbon compounds or hydrocarbon mixtures of relatively narrow rangethan whatever intermediate reactions are involved, there is an overallloss of hydrogen, a tendency to carbon separation and a generally widerboiling range in the total liquid products as compared with the originalcharge. Under mild cracking conditions involving relatively lowtemperatures and pressures andshort times of exposure to crackingconditions it is possible to some extent to control cracking reactionsso that they are limited to primary decompositions and there .is aminimum loss of hydrogen and a maximum production of low boilingfractions consisting of compounds representing the fragments of theoriginal high molecular weight compounds.

As the conditions of pyrolysis are increased in severity using highertemperatures and higher t'mes of exposure to pyrolytic conditions, thereis a progressive increase in loss of hydrogen and 4 a large amount ofsecondary reactions involving recombination of primary radicals to formpolymers and some cyclization to form naphthenes and aromatics, but themechanisms involved in these cases are of so complicated a nature thatvery little positive information has been evolved in spite of the largeamount of experimentation which has been done and the large number oftheories proposed. In general, however, it may be said that, startingwith paraflin hydrocarbons representing t e highest degree ofsaturation, these compounds are changed progressively into olefins,naphthenes, aromatics, and finallyinto carbon and hydrogen and otherlight fixed gases.

- It is not intended to infer from this statement that any particularsuccess has attended the con for the decomposition very rapid rate,necessitating theuse of extremely carbon pyrolysis is hydrocarbon intoan aromatic hydrocarbon of the same number of carbon atoms by way of theprogressive steps shown. Ii this is done it is usually with very lowyields which are of very little practical significance.

The search for catalysts to specifically control and accelerate desiredconversion reactions among hydrocarbons has been attended with the usualdifliculties encountered in finding catalysts for other types ofreactions since thereare no basic laws or rules for predictingtheeffectiveness of catalytic materials and the art as a whole is in amore' or less empirical state. In using catalysts even in connectionwith conversion reactions among pure hydrocarbons and particularlyin'connection with the conversion of the relatively heavy dlstillatesand residua which are available for cracking, there is a generaltendency reactions to proceed at a short time factors and very accuratecontrol of temperature and pressure to avoid too extensivedecomposition. There are further difficulties encountered in maintainingthe efllciency of catalysts employed in pyrolysis since there is usuallya 'rapid deposition of carbonaceous materials on their surfaces and inthelrpores.

The foregoing brief review of the art oi hydrogiven to furnish a generalbackground for indicating the improvements in suchprocesses which areembodied in the present invention, which may be applied to the treatmentof pure paraflin or olefin hydrocarbons,

hydrocarbon mixtures containing substantial percentages of parafllnhydrocarbons such as relatively close cut fractions producible bydistilling petroleum, and analogous fractions which contain unsaturatedas well as saturated straight chain hydrocarbons, such fractionsresulting from cracking operations upon the heavier fractions ofpetroleum.

In one specific embodiment, the present invention comprises theconversion of aliphatic hydrocarbons including paraflln and olefinhydrocarbons into aromatic hydrocarbons by subjecting them'at elevatedtemperatures of the order of 400-700 C. to contact for definite times ofthe order of 6-50 seconds with catalytic materials comprising major.proportions of refractory carriers of relatively low catalytic activitysupporting minor proportions of compounds of elements selected fromthose occurring in the lefthand column of group IV of the periodictable, the;

.tact, temperature and pressure very high yields of the order of '15 to90% of the benzene or aromatic compounds are obtainable in the arteither with or without catalysts. rmthe sake of illustrating andexemplifying the types of hydrocarbon conversion reactions which arespecifically accelerated under the preferred conditions by the presenttypes of catalysts, the following structural equations are introduced:

n-heptane toluene cm ch ch. cur-cm ch c-cm m OHr-CHs s --cm I In the'foregoing table the structural formulas of the primary parafilnhydrocarbons have been represented as a nearly closed ring instead of bythe usual linear arrangement indicatingthepossible H n-octans involved.No

I All;

attempt has been made toindicate the possibleintermediate existence ofmono-olefins, diolefinshexamethylenes or alkylated hexam'ethylenea whichmight result from the loss of varioiu amounts of hydrogen. It isnotknown at the present time whether ring closure occurs at the loss ofone hydrogen molecule or whether dehydrogenation of the chain'carbonsoccurs so that eharacterindicatimgenerallythetype "the first ringcompound'formed is an aromatic such as bensene or oneof its derivatives.The abovethreeequationsareofarelatiyelyslmple of reactions involved butin the case of n-parailins or *mono-oleiins of higher molecular weightthan theoctane'shownandinthecaseofbranch chain compounds which containvarious alkyl substituent groups in different positions along thesix-carbon atomcha'ini'more complicated reactions will beinvolv'ed, Forexample, inthe case of such a primary as 2,3-dimethyl hexane theprincipal resultant product is apparentlyo-xyleneal'thereareconcurrently produced definite-yiel of such compoimds as ethylbenzene indicating of m substituent methyl groups. In the case ofnonanes which arerepresented by the compound 2,3,4-trimethyl hexane,there is formation not only of mesitylene but also of such compoundsquantity at a reasonable am ethyl benaol and meta propy'l ben-'Itwillbescenfromthefthatthe scope of the present invention ispreferably limited to the treatment of aliphatic hydrocarbonswhichcontain at leastficarbonatomsin straightchain ent; In the case ofcontaining less than 6- parafiin vcarbon atoms in linear ent, someformation ofaromaticsmaytakeplacedue topri- 10mary'tionreactionsalthough obviously theextentofthesewillvaryconsiderablywlth the'type of compolmd and the conditionsof operation. The process is readily applicable toparaiiinsfromhexaneuptododecaneandtheir 15 corresponding olefins. withincrease in molecular weight beyond this point the percentage of.undesirable side reactions tends to increase and yields of the desiredalkylated aromatics decrease in proportion.

The t invention is characterized by the 7 use of a particular group ofcomposite catalytic materials which employ as their base catalystscertain refractory oxides and silicates which in themselves may havesome slight specific catalytic I ability in the dehydrogenation andcan-.lization reactions but which are improved greatly in this respectby the additionv of certain promoters or secondary catalysts in minorproportions. These base supporting materials are preferably of a 80rugged and refractory character capable of vwith-.standingthesevereusetowhichthecatalysts are put in regard totemperature during service and in regeneration by means of air or otheroxidizing gas mixtures after they have become fouled 'with carbonaceousdeposits after a period of service. tsexamples of materials which-may beemployed in granular form as supports for the preferred catalvticsubstances may be mentioned the following:

Magnesium oxide Montmorlllonite clays Almninumoxide Kieselguhr BauxiteCrushed firebricl; Bentonite clays Crushed silica Glauconite (d) Itshould be emphasized that in the field of catalysis there have beenveryfew rules evolved which will enable the prediction of what materialswill catalyae agiven reaction. Most of the catalytic work has been doneon a purely empirical basis, even' though at times certain groups ofelement'siqr ,e'ompo'imds have been found to be-more in certain types ofons.

In regardtdthe basecatalytic which invention,'some.precautions w surethat they pmper physical and chemical before'they are impre n teareprefefably employedaccoi-dingiothe preselhat with the promoters torender them more efilcient.

In regard to magnesium oxide, which may be alternatively. employed'tmsis most conveniently preparedbythecalein'ationofthe mineralmagnesltewhich'is most commonly encounteredin a'massiveorearthyvarietyandrarclyincrystai form,- the crystals beingusually rhombohedral.

In many natural tes the'magnesium oxidemaybereplacedtotheextentofseveral .percentbyferrous oxide. Themineralis of quite I occurrenceand readily obtainable in figure. The pure"conipoimdbeginstodecomposetoformthe oxide at a temperature of 350' 0.,though the rate of dea ly cannon reachesapracticalvalueat' considerablyhigher tempera ures, usually of the or er of 800 C. to 900 C. Magnesiteis related to Dolomite, the mixed carbonate of calcium and magnesium,which latter mineral, however; is not of as good service as therelatively pure magnesite in the present instance. Magnesium carbonateprepared by precipitation or other chemical methods may be usedalternatively in place of the natural mineral, this permitting its useas the active constituentof masses containing spacing materials ofrelatively inert character and in some cases allowing the production ofcatalysts of higher efficiency and longer life. It is not necessary thatthe magnesite be completely converted to oxide but as a rule it is preferable that the conversion be at least over 90%, that is, so that thereis less than 10% of the carbonate remaining in the ignited material.

Aluminum oxide which is generally preferable as a base material for themanufacture of catalysts for the process may be obtained from naturalaluminum oxide minerals or ores such as bauxite or carbonates such asdawsonite by proper calcination, or it may be prepared by precipitationof aluminum hydrate from solutions of aluminum sulfate or differentalums, and dehydration of the precipitate of aluminum hydroxide by heat,and usually it is desirable and advantageous to further treat it withair or other gases, or by other means to activate it prior to use.

Two hydrated oxides of aluminum occur in nature, to-wit, bauxite havingthe formula A12O3.2H2O and diaspore A12O3.H2O. In both of these oxidesiron sesqui-oxide may partially replace the alumina. These two mineralsor corresponding oxides produced from precipitated aluminum hydroxideare particularly suitable for the manufacture of the present type ofcatalysts and in some instances have given the best results of any ofthe base compounds whose use is at present contemplated. The mineraldawsonite having the formula Na3Al(C03)3.2Al(OH)3 is another mineralwhich may be used as a source of aluminum oxide.

It is best practice in the final steps of preparing aluminum oxide' as abase catalyst to ignite for some time at temperatures within the sameapproximate range as those employed in the ignition of magnesite,to-wit, from BOO-900 C. This probably does not correspond to com-' pletedehydration of the hydroxides but apparently gives a catalytic materialof good strength and porosity so that it is able to resist for a longperiod of time the deteriorating effects of the service and regenerationperiods to which it is subjected. In the case of the clays which mayserve as base catalytic materials for supporting promoters, the bettermaterials are those which have been acid-treated to render them moresiliceous. These may be pelleted or formed in any manner before or afterthe addition of the promoter catalyst since ordinarily they have a highpercentage of fines. The addition of certain of the promoters, however,exerts a binding influence so that the formed materials may be employedwithout fear of structural deteriora- I 10% by weight of the carrier. Itis most common practice to utilize catalysts comprising 2 to 5% byweight of these compounds, particularly their lower oxides.

The promoters which are used in accordance with the present invention toproduce active catalysts of the base materials include generallycompounds and more particularly oxides of the elements in the lefthandcolumn of group IV of the periodic table including titanium, zirconium,

cerium, hafnium and thorium. In general practically all of the compoundsof the preferred elements will have some catalytic activity though as arule the oxides and particularly the lower oxides are the bestcatalysts. Catalyst composites may be prepared by utilizing the solublecompounds of the elements in aqueous solutions,

from which they are absorbed by granular carriers or from which they aredeposited upon the carriers by evaporation of the solvent. The inventionfurther-comprises the use. of catalyst composites made bymixing'relatively insoluble compounds with carriers either in the wet orthe dry condition. In the following paragraphs some of the compounds ofthe elements listed above are given which are soluble in water and whichmay be used to add catalytic material to carriers. The known ,oxides ofthese elements are also listed.

'IrrAN'mu Compounds which will ultimately yield titanium catalysts onheating to a proper temperature are absorbed by stirring them with warmaqueous solutions of soluble titanium compounds, such as for exampletitanium nitrate having the formula 5TiO2.N2O5.6H2O, which issufliciently soluble in warm water to render it readily utilizable as asource of titanium oxides. Other soluble compounds which may be used toform catalytic deposits containing titanium are the various alkali metaltitanates. Other compounds of titanium acids, including compounds of thealkaline earth and heavy metals may be distributed upon the carriers bymechanical mixing either in the wet or the dry condition. The loweroxides are generally the best catalysts. The oxide resulting from thedecomposition of such compounds as the nitrate and the hexahydrate'isfor the most part the dioxide 'IiOz. This oxide, however, is reduced byhydrogen, or by the gases and vaporous products resulting from thedecomposition of the mono-olefins treated-in the first stages of thereactions so. that the essential catalyst for the larger portion of theperiod of serviceis the sesquioxide TizO3.

ZIRCONIUM The soluble compounds of zirconium which may be used asprimary sources of catalytic materials in aqueous solution include theslightly soluble zirconium ammonium fluoride, the tetrachloride, thefluoride, the iodide and particularly the more soluble selenate andsulfate. The crystalline selenate has the formula ZI(S8O4)2.4H2O and thesulfate which is the more soluble of the two, has the formulaZr(SO4)2.4H2O. As in the case of the other alternative elements thetetrahydroxide may be precipitated from a solution of the sulfate orother soluble salt onto the surface and into the pores of an activegranular carrier by the addition of alkaline carbonate or hydroxideprecipitants, after which the zirconium hydroxide is ignited to producethe dioxide. The principal oxide of zirconium is the dioxide and thereis little evidence to indicate the existence Ill of a monoxide since thedioxide is not reducible by hydrogen at moderate temperatures and it hasbeen shown that carbon in the electric furnace reduces the dioxidedirectly to the metal.

Cmmu

A properly prepared and activated carrier is ground and sized to producegranules of relatively small mesh of the approximate order of from 4 to20 and these may be caused to absorb compounds which will ultimatelyyield compounds of cerium on heating to a proper temperature by stirringthem with warm aqueous solutions/of soluble cerium compounds, such asfor example cerium nitrate having the formula CE(NO3)3.6H2O, which issufliciently soluble in warm water to render it readily utilizable as asource of cerium oxides. Other soluble compounds which may be used toform catalytic deposits containing cerium are the various alkali metalcerous nitrates, such as for example sodium cerous nitrate having theformula 2NaNO3.Ce(NOa) 3.H2O. Other compounds of ceric acids, includingcompounds of the alkaline earth and heavy metals, may be distributedupon the carrier by mechanical mixing either in the wet or the drycondition. As 'a rule the lower oxides including the trioxide C803, thedioxide C602, the heptoxide C8407, and sesquioxide C6203. The dioxideresults from the ignition of cerous nitrate, cerous sulfate, cerouscarbonate or cerous oxalate and also from-the ignition of ceric nitrate,ceric sulfate or ceric hydroxide. Hydrogen reduces the dioxide to theheptoxide, and it is probable that this oxide plus a certain amount of te sequioxide are active catalysts.

HAFNIUM In general the properties of hafnium from a chemical and to someextent a catalytic stand point are intermediate between those ofzirconium and thorium though in most reactions hafnium compounds moreclosely correspond to those of zirconium. There is but one known oxide,the dioxide HfOz and this oxide is not readily reducible and probablyexists as such when used in minor proportions as a constituent of.catalyst composites in hydrocarbon dehydrogenation reactions. Solublecompounds of hafnium include the oxychloride having the formulaHfOC12.8H2O and the oxalate which is soluble in an excess of oxalicacid. The mixing of this oxalate solution with the miscellaneouscarriers proposed and the evaporation of the solution gives a residualmaterial which can be ignited to leave a residue of the dioxide. Hafniumsulfide catalysts may be developed by ignitpounds are seldomcommercially utilizable although the oxide in particular has been foundto exert a good catalytic influence in the types of reactions underconsideration.

THORIUM used as the tetrahydrated or dodecahydrated salt. From any ofthe soluble. salts mentioned the tetrahydroxide Th(0I-I)4 may beprecipitated by the use of alkali carbonates or alkali hydroxides andthen ignited tov produce the dioxide. The phosphates and sulfates andthe sulfide are relatively insoluble and may be incorporated with thecarrier particles either in the wet or the dry condition. The nitratemay be directly ignited, of course, to produce the dioxide.

While the identification of some other oxides of thorium such as thepentatrioxide Th305 and the monoxide Th0 has been claimed as well as aperoxide having the formula ThzO-J, it has been shown that the principaloxide catalyst in op-' erations of thepresent character is the ordinarydioxide. It is to be emphasized that the oxide is the preferred catalystsince in general it exhibits greater and more selective catalytic actionthan any other compounds which may be formed upon the carrier surfaces.

The most general method for adding promoting materials to the preferredbase catalysts,

which if properly prepared have a high adsorptive capacity, is to stirthe prepared granules of from approximately 4 to 20 mesh into solutionsof salts which will yield the desired promoting compounds on ignitionunder suitable conditions. In some-instances the granules may be merelystirred in slightly warm solutions of salts until the dissolvedcompounds have been retained on the particles by absorption orocclusion,'after which the particles are separated from the excesssolvent by settling or filtration, washed with water to remove excesssolution, and then ignited to produce the desired residual promoter. Incases of certain compounds of relatively low solubility it may benecessary to add the solution in successive portions to the adsorbentbase catalyst with intermediate heating to drive off solvent in order toget the required quantity of promoter deposited upon the surface and inthe pores of the base catalyst. The temperatures used for drying andcalcining after the addition of the promoters from solutions will dependentirely upon the individual characteristics of the compound added andno general ranges of temperature can be given for this step.

In some instances promoters may be deposited from solution by theaddition of precipitantswhich cause the deposition of precipitates uponthe catalyst granules. As a rule methods of mechanical mixing are notpreferable though in some instances in the case of hydrated or readilyfusible compounds these may be mixed with the proper proportions of basecatalysts and uniformly distributed during the condition of fusingor-fluxing.

In regard to the relative proportions of base catalyst and promotingmaterials it may be stated in general that the latter are generally lessthan 10% by weight of the total composites. The effect upon thecatalytic activity of these base catalysts caused by varying thepercentage of any given compound or mixture of compounds depositedthereon is not a matter for exact calculation but more one fordetermination by experiment. Frequently good increases in catalyticeffectiveness are obtainable by the deposition of as low as 1% or 2% ofa promoting compound upon the surface and in the pores of the basecatalyst, though the general average is about 5%.

It has been found essential to the production of high yields ofaromatics from aliphatic hydrocarbons when using the preferred types ofcatalysts that depending upon the. aliphatic hydrocarbon or mixtures ofhydrocarbons being treated, temperatures from 400- 700- C. should beemployed, contact times of approximately 6 to 50 seconds and pressuresapproximating atmospheric. The use of subatmospheiic pressures of theorder of atmosphere may be beneficial in that reduced pressuresgenerally favor selective dehydrogenation reactions but on the otherhand moderately superatmospheric pressures usually of the order of lessthan 100 pounds per square inch tend to increase the capacity ofcommercial plant equipment so that in practice a balance is struckbetween these two factors. The times of contact most commonly employedwith n-paraflinic or mono-olefinic hydrocarbons having from 6-12 carbonatoms to the molecule are of the order of 6-20 secs. It will beappreciated by those familiar with the art of hydrocarbon conversion inthe presence of catalysts that the factors of temperature, pressure andtime will frequently have to be adjusted from the results of"preliminary experiments to produce the best results in any giveninstance. The criterion of the yield of aromatics will serve to fix thebest conditions of operation. In a general sense the relations betweentime, temperature. and pressure are preferably adJusted so that ratherintensive conditions are employed of sufilcient severity to insure amaximum amount of the desired cyclization reactions with a minimum ofundesirable side reactions. If

too short times of contact are employed the conversion reactions willnot proceed beyond those of simple dehydrogenation and the yields ofolefins and diclefins will predominate over those of aromatics. i

While thepresent process is particularly-applicable to the production ofthe corresponding aromatics from an aliphatic hydrocarbon or a mixtureof aliphatic hydrocarbons, the invention may also be employed to producearomatics from aliphatic hydrocarbon mixtures such as distillates fromparafllnic or mixed base crude petroleum.-

tive solvents such as liquid sulfur dioxide, alcohols, furfural,chlorex, etc.

In operating the process the general procedure is to vaporizehydrocarbons or mixtures of hydrocarbons and after heating the vapors toa suitable temperature within the ranges previously specified, to passthem through stationary masses of granular catalytic material invertical cylindrical treating columns or banks of catalyst-containingtubes in parallel connection. Since the reactions are endothermic itmaybe necessary to apply some heat externally to maintain the bestreaction temperature. After passing through the catalytic zone theproducts are submitted to fractionation to recover ,cuts or fractionscontaining the desired aromatic product with the separation of fixedgases, unconverted hydrocarbons and heavier residual materials, whichmay be disposed of in any suitable manner depending upon theircomposition. The overall yield of aromatics may be increasedby recyclingthe unconverted straight chain hydrocarbons further treatment with freshmaterial, although this is a more or less obvious expedient and notspecifically characteristic of the present invention.

It is an important feature of the present process that the vaporsundergoing dehydrogenation should be free from all but traces of watervapor since the presence of any substantial amounts of steam reduced thecatalytic selectivity of the composite catalysts to a marked degree. Inview of the empirical state of the catalytic art, it is not intended tosubmit a complete explanation of the reasons for the deleteriousinfluence of water vapor on the course of the present type of catalyzedreactions, but it may be suggested that the action of the steam is tocause a partial hydration of such basic carriers as alumina andmagnesium oxide and some of the active catalytic compounds due topreferential adsorption so that in effect the hydrocarbons are preventedfrom reaching or being adsorbed by the catalytically active surface.

The present types of catalysts are particularly eifective in removinghydrogen from chain compounds in'such a way that cyclization may bepromoted without removal of hydrogen from end carbon atoms so that bothend and side alkyl groups may appear as substituents in benzene ringsand it has been found that under proper operating conditions they do nottend to promote any great amount of undesirable side reactions leadingto the deposition of carbon or carbona-- ceous materials and for thisreason show reac'- tivity over relatively long periods of time. Whentheir activity begins to diminish after a period of service, it isreadily regenerated by the simple expedient of oxidizing with air orother oxidizing gas at a moderately elevated temperature, usually withinthe range employed in the dehydrogenation and cyelization reactions.This oxida- I tion eflectively removes traces of carbon deposits whichcontaminate the particles and decrease their efficiency. It ischaracteristic of the present types of catalysts that they may berepeatedly regenerated. with only a, very gradual loss of catalyticefllcienfly- During oxidation with-air or other oxidizing gas mixture inregenerating partly spent material, there 'isevidence to indicate thatwhen the lower oxides are employed, they are to a large.

extent, if not completely,- oxidized to higher oxides which combine withbasic carriers to form compounds of variable composition. Later thesecompounds are decomposed byicontact with reducing gases in the firststages of service to reform the lower oxides and regenerate ,the realcatalyst and hence the catalytic activity.

Emmple I v A n--hexane charge obtained bythe careful fractionation of aPennsylvania crude oil was found to have a boiling point of 68.8 C., anda refractive index of 1.3768 which corresponds closely to the propertiesof the pure compound. The general procedure for manufacturing thecatalyst was to dissolve titanium nitrate in cold water and utilize thissolution as a means of eventually adding titanium oxides to a carrier. Asaturated solution of titanium nitrate in 100 parts of water wasprepared and the solution was then added to about 250 parts by weight ofactivated alumina which had been produced by calcining bauxite at atemperature of about 100 C.,

followed by grinding and sizing to produce par-,

ticles of approximately. 8-12 mesh. Using the proportions stated, thealumina exactly absorbed f5 thesolutionand theparticleswereflrstdriedat100 6.,for about two hours and thetemperature wasthenraisedto350C.,inaperlodofeighthours. After thiscalcining treatment'theparticleswereplacedlnareactionchamberandthetitaniumoxidureducedinacurrentofhydrogen at about 500 (1., when theywerethenreaewfor Thehexanewasvaporisedandpassedoverthegranularcatalystpreparedas descrlhed.using a of515C.,substantlallyatmospheflc pressure,andatimeofcontactof 18secs. Theyieldofpurebenseneunderthueconditionswasfoundtobe47%lryweislitofthenormaln-hexanecharged.Byrecyclingoftheunconverted material the ultimate yield of benzene wasraised to 77%.

. sample II catalyst as in Example-I at a temperature of 560 0.,substantially atmospheric pressure and 13 secs. contact time. 'lhe yieldof toluene on a once-through basis was foundvto be 48%-by weight andagain it was found that by recycling the unconverted n-heptane that theyield of the adit ionsandby -'2100C..fol:abo|ittwohoursandttletempera-'ld eairodtoluenecouldultintatelybebrought to sample 111' 1'0 manufacturegranularcatalyst particles, activated alumina prepared by calcln'aflonat a temperature of about 1500 R, (the particlesvaryinginsisefromapproximately 10 tomesh) were stirred in a moderatelysaturated solution of zirconium sulfate while adding a solution ofUslngacatalystmmredgena'ailyinaccord- "ance with the procedureoutlined-in Example 111, n-heptane wassubmittedtoconversion conditionscomprising a temperature of 555 0., at-

time. A5096 yieldoftohienewasobtainedin theflrstpassoverthecatalyatunderthese coni'ecyclingtheultimate yieldwas broughtto about 75%.

tumble Vthecatalystwastodimolvecerousnitrateinwaterandutilisethissolutlonasameansofaddingceriumoxidestoacarrler. 2ilpartsby-weight ofcerousnitrate wasdisaolv'edinabout 100 parts by weight of water, and the solution wasthen addedtoabout250-parts'byweightoiactivated alumina which had beenproduced by calcining bauxite at a temperature of about 700- C., fol--lowedbygrindingandsislngtoproducepartb' cl cofapproximately 8-12mesh.Usingtheproportionsstated the aluminaexactlyabsorbed-thesomtionandtheparticleswereiirstdriedatn-Heptanewastreatedwiththesametypeof sodium hydroxide to precipitatezirconium hy-' mospheric and about 15 seconds contact The generalprocedure in thepreparation of,

turewas tbenraisedto350 cam er-10a of eight hours. After this calciningtreatment the particles were placedin a reaction chamber and the,

tially atmospheric pressure. and a time of con-'- tact of 21 seconds.'I'he yield of pure benzene under these conditions was found to be 44%by weight of the normal n-hexane charged. By recycling of theunconverted material the ultimate yield of benzene was raised to 74%.

Example VI n-Heptane was treated with the same type of catalyst as inExample V at a temperature of 570 0., substantially atmospheric pressureand 18 seconds contact time. The yield of toluene on a once-throughbasiswas found to be 44% by weight and again it was found that by recyclingthe unconverted n-heptane that the yield of the desired toluene couldultimately be brought to 74%.

Emmple VII As an example of the manufacture of aromatic hydrocarbons bydehydrogenation and cyclintion of mono-oleflns, the case of l-heptanemay be considered. A catalyst wasemployed which was manufactured by thesame general procedure givenin Example I and the vapors of the n-heptanewere passed over the granularc'atalyst at a temperature of 500 0.,substantially atmospheric pressure and 15 secs. contact time. Aonce-through yield of toluene amounting to 75% by weight of the heptanecharged was obtained which was positively identified by its conversionto the dinitro compound which melted sharp at -66 C.

Example VIII Y This example is introduced to indicate the possibilitiesin manufacturing benzol from hexenes according to the present process.Using azirconium oxide catalyst. prepared generally in accordance withthe procedure outlined in Exam: pic 11:, l-hexene was over the granularmaterial at a temperature of 505 C., atmospheric pressure and about 18seconds contact time. The yield of bensol was approximately in a singlepass and this could be increased to substan-' hydrocarbonsfrom-aliphatic hydrocarbons of from six to twelve carbon atoms, whichcomprises dehydrogenating and cyclicizing the aliphatic hydrocarbon bysubjection to a temperature of the order of 400 to 700 C., for a periodof about 6 to 50 seconds, in the presence of a compound of a metal fromthe left hand columnof group IV of the periodic table and selected fromthe class consisting oi titanium, zirconium, cerium, hafnium andthorium.

2. A process for the production of aromatic hydrocarbons for aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the aliphatic hydrocarbon by subjectionto a temperature of the order of 400 to 700 C., for a period of about 6to 50 seconds, in the presence of an oxide of a the periodic table andselected from the class consisting of titanium, zirconium, cerium,hafnium and thorium.

3. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the aliphatic hydrocarbon by subjectionto a temperature of the order oi 400 to 700 0., for a period of about 6to 50 seconds, in the presence of a solid granular catalyst comprisingessentially a major proportion of a carrier of relatively low catalyticactivity supporting a minor proportion of a compound of a metal from theleft hand column of group IV of the periodic table and selected from theclass consisting of titanium, zirconium, cerium, hafnium and thorium.

4. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the aliphatic hydrocarbon by subjectionto a temperature of the order of 400 to 700 C., for a period of about 6to 50 seconds, in the presence of a solid granular catalyst comprisingessentially a major proportion of a carrier of relatively low catalyticactivity supporting a minor proportion of an oxide of a metal from theleft hand column of group IV of the periodic table and selected from theclass consisting of'titanium, zirconium, cerium, hafnium and thorium.

5. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons 01 from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the allphatic hydrocarbon by subjectionto a tempera ture of the order of 400 to 700 C., for a time period ofless than 50 seconds but sufllcient to dehydrogenate and cyclicize thealiphatic hydrocarbon, in the presence of a compound of a metal from theleft hand column of group IV of the periodic table and selected from theclass consisting of titanium, zirconium, cerium, hafnium and thorium.

6. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the aliphatic hydrocarbon by subjectionto a temperature of the order of 400 to 700 C., for a time period ofless than 50 seconds but sufficient to dehydrogenate and cyclicize thealiphatic hydrocarbon, in the presence of an oxide of a metal from theleft hand column of group IV of the periodic table and selected from theclass consisting of titanium, zirconium, cerium, hafnium and thorium.

7. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the aliphatic hydrocarbon by subjectionto a temperadehydrogenate and cyclicize the aliphatic. hydrocarbon, inthe presence of a solid granular catalyst comprising essentially a majorproportion of a carrier of relatively low catalytic activity supportinga minor proportion of a compound of a metal from the left hand column ofgroup IV of the periodic table and selected from the class consisting oftitanium, zirconium, cerium, hafnium and thorium.

8. A process for the production of aromatic hydrocarbons from aliphatichydrocarbons of from six to twelve carbon atoms, which comprisesdehydrogenating and cyclicizing the allphatic hydrocarbon by subjectionto a temperature of the order of 400 to 700 C., for a time period ofless than 50 seconds but sumcient to dehydrogenate and cyclicize thealiphatic hydrocarbon, in the presence of a solid granular catalystcomprising essentially a major proportion of a carrier of relatively lowcatalytic activity supporting a minor proportion of an oxide of a metalfrom the left hand column of group IV of the periodic table and selectedfrom the class consisting of titanium, zirconium, cerium, hafnium andthorium.

JACQUE C. MORRELL.

